The ultrastructure of the marine blue green alga,Trichodesmium erythraeum,with special reference to the cell wall,gas vacuoles,and cylindrical bodies

Summary The marine blue green alga, Trichodesmium erythraeum, was studied with electron microscopy in an attempt to elucidate the structural basis for its rapid lysis when removed from its marine environment. In this connection, it was found that a thining of the electron-dense layer of the longitudinal wall at the site adjacent to transverse wall attachment was responsible for lysis. The underlying biochemical basis for this change has not been elucidated because of the extreme difficulties of maintaining and growing the alga in culture under defined conditions. Several other features of considerable interest also were found. Especially interesting is the very regular array of gas vacuoles in the form of a hollow cylinder which shields most of the photosynthetic system. It was suggested that the gas vacuoles might possibly function optically, having adaptive value in protecting the free-floating alga from excessive radiation. In addition, a detailed structure of the cylindrical bodies was presented, and its structure with the photosynthetic lamellae was compared. On the basis of sectoring to form fragments of double lamellar units from the cylindrical body which are identical in structure to the photosynthetic lamellae, it has been postulated that the cylindrical body may be the site of synthesis for the photosynthetic system in Trichodesmium erythraeum.     

Gene-Enzyme Relationships in Neurospora Invertase

A spontaneous, single-gene mutation responsible for a total lack of invertase activity in Neurospora crassa is described. The mutation is believed to lie in the structural gene for invertase, since an immunologically cross-reacting protein is made by the mutant strain. In addition, there was no evidence for a defect in regulation of invertase activity or synthesis by the following criteria. (i) The invertaseless condition was recessive in heterokaryons; (ii) no invertase inhibitor was found in mutant extracts by mixing experiments; and (iii) none of the several sugars able to induce activity in wild-type strains was able to induce activity in the mutant strain. It was also discovered that most of the wild-type enzyme (55 to 75%) cannot be washed free from the rapidly sedimenting cell debris. This finding provided additional support for the hypothesis that Neurospora invertase is located within or about the cell wall.     

Cardiac Monitoring in a Community Hospital—Analysis of 18 Months' Experience

Cardiac monitoring facilities have been present in teaching hospital centers for over five years. A substantial decrease in mortality has been observed in monitored patients with acute myocardial infarction. The community hospital system offers a challenge to effective monitoring since many physicians care for patients and often many kinds of therapy are used.After 18 months of operation mortality from myocardial infarction was only 16.6 percent in a community hospital monitoring unit where the majority of the emergency care and resuscitation was carried out by nurses. Vital to this success was the use of standing orders for nurses, requirement of privilege to practice within the monitoring facility and acceptance of the nurse as a therapist in emergency situations.Fourteen patients were successfully resuscitated and were later discharged from the hospital. Four of them had ventricular fibrillation from digitalis intoxication.Patients with shock and severe congestive heart failure continue to be a major unsolved clinical problem. The results indicate that the potentially viable patient with serious electrical disturbances can almost invariably be salvaged.     

Gammaphotography

The Anger scintillation camera greatly broadens the range of studies performed by radioisotope imaging devices. Its ability to view in any direction, to make an image simultaneously of an entire field of view, and to obtain images rapidly, all serve to make scintiphotography analogous to fluoroscopy. Illustrations of its uses in static and dynamic gammaphotography and in numerical data processing are described.     

Tryptophan Synthetic Pathway and Its Regulation in Chromobacterium violaceum

Extracts of Chromobacterium violaceum catalyzed all of the reactions involved in synthesizing tryptophan from chorismic acid. Tryptophan auxotrophs which had lost any of these activities did not produce the characteristic purple pigment, violacein, when grown on a medium in which tryptophan was limiting. Gel filtration of extracts allowed us to estimate molecular weights for the tryptophan enzymes. All of the enzymes appeared to have molecular weights below 100,000. No enzymes were observed to occur in aggregates. The specific activities of the enzymes of the tryptophan pathway did not change when mutants were grown under conditions of limiting or excess tryptophan. The first enzyme in the pathway, anthranilate synthetase, was subject to feedback control by the end product, tryptophan. Tryptophan acted as a noncompetitive inhibitor with respect to glutamine, one of the substrates for anthranilate synthetase, and as a competitive inhibitor of the reaction when chorismate, the other substrate, was varied. The nonlinearity observed in the Lineweaver-Burk plot in the latter case suggests that there may be more than one chorismate-binding site on anthranilate synthetase.     

Metabolic Changes in Nicotinamide Adenine Dinucleotide in Response to Anthrax Toxin

Bacillus anthracis produces a toxin both in vitro and in vivo which, when injected intravenously into rats, brings about the death of the animals accompanied by gross pulmonary edema. Lung tissue removed prior to death showed, in vitro, a 30% reduction in overall oxidative metabolism (Q(o2)), whereas the nicotinamide adenine dinucleotide (NAD)-independent succinic dehydrogenase remained unaffected. The NAD concentration in the lungs of injected animals was reduced by 50%. Upon addition of NAD, the Q(o2) of lung tissue from injected animals rose to control values. At 45 min after toxin injection, the serum lactate concentration began to rise, showing about a 3.5-fold increase over controls after 75 min. No changes occurred in the pyruvate concentration. These changes may be explained by increased use of the pyruvate for glycolytic energy production with further loss of NAD. Additional experiments with liver, spleen, kidney, and brain tissues showed that the toxin-induced reduction of Q(o2) is an effect specific for lung tissue. Brain tissue showed a significant increase in oxidative metabolism upon the addition of the toxin, whereas the other tissues remained unaffected. It is suggested that a principal effect of the toxin is to inhibit, in lung tissue, the regeneration of NAD in the respiratory chain.     

Medicine in Society—Part I: Change and Challenge

The Committee to Study the Role of Medicine of the California Medical Education and Research Foundation (CMERF) is grateful to Dr. Watts for the following paper which served as the philosophical basis for the Committee''s study and discussions. The Committee is also grateful to CMERF and to its president, James C. Doyle, for the encouragement and cooperation it has received in the course of its intensive study of a problem which is of great interest and concern to the medical profession of California.Dr. Watts'' background paper has served as a potent stimulus in directing the Committee''s attention to the continuing dialogue between medicine and society, and in focussing on problems and issues which will be the subject of the Committee''s Second Progress Report, excerpts from which are scheduled for publication in the next issue of California Medicine.